1. Field of the Invention
The present invention relates to an expanding sleeve anchor used in a concrete wall and a structure for enhancing the anchoring capability thereof.
2. Description of the Related Art
A first conventional expanding sleeve anchor structure used in a concrete wall in accordance with the prior art is shown in FIGS. 1 and 2. The expanding sleeve anchor structure comprises a nail base tube 3 provided with a plurality of separating lines 31 and an urging bolt 11 fitted with a tapered head 111, extending through the nail base tube 3. When the expanding sleeve anchor is inserted into cavity 41 of concrete wall 4, tapered head 111 is pressed into the nail base tube 3, and the separating lines 31 are urged outward, thereby securing the nail base tube 3 in the cavity 41 of the concrete wall 4.
A second conventional expanding sleeve anchor structure used in a concrete wall in accordance with the prior art is shown in FIGS. 3 and 4. The expanding sleeve anchor structure comprises a nail base tube 3 inserted into a cavity 41 of the concrete wall 4 and provided with a plurality of separating lines 31, a bolt 21 extending through the nail base tube 3, and an urging nut 22 screwed on the bolt 21 to be pressed into the nail base tube 3 for urging the separating lines 31 outward, thereby securing the nail base tube 3 in the cavity 41 of the concrete wall 4.
As shown in FIG. 5, the conventional nail base tube 3 includes a plurality of front end guide inlets 32 for allowing entrance of the tapered head 111 of the urging bolt 11 as shown in FIG. 2 or the urging nut 22 as shown in FIG. 4 into the nail base tube 3. However, the front end guide inlets 32 of the conventional nail base tube 3 have a large forging face so that the tapered head 111 of the urging bolt 11 or the urging nut 22 is not easily pressed into the conventional nail base tube 3 through the front end guide inlets 32.